Summary :
Exchanges, travel, intercountry adoption which has become an increasingly common practice, uprooting, etc. have disrupted the compositions of increasingly multilingual socie­ties and families. The development of research in cognitive sciences and the birth of bilingualism as a field of study since the 1970s, together with recent advances in linguistics, psycho­logy, neuroimaging and speech therapy have made it possible to better describe the neuropsychological function and develop­ment of the bilingual person, particularly in the development of the normo and hearing-impaired child, in both language and behavior. It also involves other pathological situations such as stuttering and autism seen in Alzheimer's disease. Bilingualism is now a recognized cultural, social, educational and professio­nal substantial asset. Children who are able to express them­selves in more than one language see their metalinguistic skills increase and show a stronger attachment to their parent's culture of origin.